The Afterglows and Host Galaxies of Short GRBs: An Overview

Abstract

Despite a rich diversity in observational properties, gamma-ray bursts (GRBs) can be divided into two broad categories based on their duration and spectral hardness -- the long-soft and the short-hard GRBs. The discovery of afterglows from long GRBs in 1997, and their localization to arcsecond accuracy, was a watershed event. The ensuing decade of intense study led to the realization that long-soft GRBs are located in star forming galaxies, produce about 10^51 erg in collimated relativistic ejecta, are accompanied by supernovae, and result from the death of massive stars. While theoretical arguments suggest that short GRBs have a different physical origin, the lack of detectable afterglows prevented definitive conclusions. The situation changed dramatically starting in May 2005 with the discovery of the first afterglows from short GRBs localized by Swift and HETE-2. Here I summarize the discovery of these afterglows and the underlying host galaxies, and draw initial conclusions about the nature of the progenitors and the properties of the bursts.